Multi-layer composite materials are known from the prior art. The Korean publication with the number 10 2005 0027702 A, for example, discloses a roof element of a vehicle body, in which a three-layer composite material provided with a turn-up is arranged. The composite material, in this case, has a core layer made of a synthetic resin, in particular polypropylene. Generally, an advantageous balance between the weight and the rigidity or, respectively, the strength of the composite material is provided by means of the core layer made of a plastics material and the two cover layers made of a metallic material. The stress on the core layer is less in the case of typical loads than that on the cover layer, so that a plastics material which is substantially distinguished by its low density compared to metal materials, and therefore its lower weight, can be selected for the core layer. Moreover, composite materials of this type have heat-insulating and vibration-damping properties.
The German published application 1 527 957 in turn discloses a three-layer composite material with two outer sheet metal layers and a core layer made of a plastics material, for example polyvinyl acetate provided with additives, which is deep-drawn. In order to reduce the viscosity of the plastics material core layer, the deep-drawing process should take place at a temperature of 120° C. to 160° C. It should be possible to increase the limit drawing ratio, in particular, by this measure. The forming radii produced during the deep-drawing are, however, significantly larger relative to the radii of turn-ups or beading folds, respectively, which is why the stress on the material of the individual layers is significantly less in the region of the forming bend during deep-drawing than during the incorporation of a beading fold or turn-up. As the plastics material core layer, in contrast to DE 1 527 957, also generally has a significantly greater thickness than the cover layers, the cover layers are disproportionately susceptible with respect to loading exerted during forming, and therefore a material failure, for example ruptures, cracks or the like can occur on the cover layers.